1. Field of the Invention
The present invention relates to an organic light-emitting device.
2. Description of the Related Art
Recently, organic light-emitting devices, which are self-light-emitting devices, have attracted attention as a flat panel display. In organic light-emitting devices, the presence of moisture or oxygen readily causes degradation of characteristics thereof. Even a trace amount of moisture causes, for example, a separation of an organic compound layer from an electrode layer, resulting in generation of dark spots. Therefore, an organic light-emitting portion is typically covered with an etching glass cover, a sealing agent is applied on the periphery of the organic light-emitting portion, and a moisture absorbent is placed inside thereof so that moisture intruding from the sealing surface is absorbed by the moisture absorbent, thereby ensuring the lifetime of an organic light-emitting device. However, in order to realize a space-saving flat panel display including a thin organic light-emitting device, it is necessary to eliminate the space taken up by the moisture absorbent and to provide a thinner organic light-emitting device. Consequently, a method of sealing an organic light-emitting device that does not require a large amount of moisture absorbent has been desired. Therefore, a highly functional sealing layer for preventing moisture and oxygen from intruding into the organic compound layer has been desired.
To solve these problems, recently, a sealing layer composed of a silicon oxynitride film formed by chemical vapor deposition (CVD) or sputtering, and a sealing layer prepared by stacking a ceramic film and an organic film have been proposed as sealing layers of organic light-emitting devices.
Japanese Patent Laid-Open No. 2000-223264 proposes a structure in which a first inorganic sealing layer, a resin sealing layer, and a second inorganic sealing layer are stacked in that order. This patent document describes that an organic electroluminescent (EL) element which has low residual stress and in which moisture can be satisfactorily blocked can be provided.
Japanese Patent Laid-Open No. 2003-223992 proposes a structure in which an organic light-emitting layer is covered with an inorganic film, and a color filter formed on a cover plate is disposed at a position distant from an organic EL element. This patent document describes that degradation of an organic EL layer caused by moisture or a gas component generated from the color filter can be suppressed.
As described in these patent documents, when a sealing layer for preventing the intrusion of moisture and a gas component is formed of an inorganic film or stacked layers including an inorganic film, moisture and the gas component can be prevented from intruding into an organic light-emitting layer via the sealing layer.
However, in the patent documents cited above, moisture and a gas component that intrude from the edge of the organic light-emitting device to the organic light-emitting layer are not considered. The present inventors have found that even when a sealing layer having excellent moisture-proof property is disposed on a light-emitting portion as a component for preventing moisture intrusion or the like, which causes degradation of the organic light-emitting device, moisture can intrude from the interface between the sealing layer and a layer adjacent to the sealing layer, thereby significantly affecting the light-emitting area.
Furthermore, in a method of producing an organic light-emitting device, electrodes and an organic layer are formed on a single substrate, a sealing layer is formed, and the substrate is then cut. Thus, a plurality of organic light-emitting devices are produced from a single substrate. The present inventors have also found that when organic light-emitting devices are produced by such a method, the sealing layer is exposed on the cut surface, and furthermore, a portion of the sealing layer is separated by the cut or cracks are formed in the sealing layer.
As described above, when the sealing layer is exposed and separation of a portion of the sealing layer or formation of cracks occurs, moisture or the like intrudes from the interface of the sealing layer or the portion where the sealing layer has been separated, thereby hindering light emission.